what do i need to launch an social network app?

hi, im kind of new to this. know the basics about app development, but i just need to pin-point what i need for a soical network app. have been dabbeling with eclipse but understand i need servers and what not. so just need a basic list over things i need to get the log in interface up and running..
i understand i need a database, and in order to get that i need a server, and to get that i need a domain. so i will need to invest money to get it....

or?

thanks in advance for any help